Catalytic steam cracking of hydrocarbons and catalysts therefor

ABSTRACT

Steam cracking of saturated hydrocarbons to form unsaturated hydrocarbons, such as ethylene, propylene, butylenes, butadiene, and aromatics, is carried out in the presence of a catalyst comprising a major proportion of oxides of zirconium or hafnium associated with active alumina together with oxides of chromium, manganese or iron and promoted with compounds of alkali metals and alkaline earth metals. High conversion efficiences are achieved at high space velocities and without carbon deposition.

United States Patent 1 Wrisberg et al. I

[4,51 Apr. 3, 1973 [54] CATALYTIC STEAM CRACKING OF HYDROCARBONS AND CATALYSTS THEREFOR [75] Inventors: Johannes Wrisberg, Gammel Holte;

Kjeld Jorn Andersen, Tulstrup; Erik Mogensen, Ramlose, all of Denmark [73] Assignees: Haldor Frederik Axel Toksoe, Frydenlundsvej Vedbaek, Denmark; Fluor Corporation, Los Angeles,

Calif.

[22] Filed: Dec. 17, 1970 [21] App]. No.: 99,271

[30] Foreign Application Priority Data Dec. 23, 1969 Great Britain ..62,552/69 [52] US. Cl. ..260/683 R, 208/122, 208/123, 208/124, 260/680 R, 260/6833 [51] Int. Cl. ..C0 7c 3/34, C10g 11/04 [58]. Field of Search 260/683, 680, 673,

[56] References Cited UNITED STATES PATENTS 2,392,750 1/1946 Linn ..260/680 2,754,354 7/1956 Kirshenbaum .....260/683.3 2,894,046 7/1959 Bloch et a]. ..260/673.5 2,941,016 6/1960 Schmetterling et a1... .....260/673.5 3,179,602 4/1965 Gremillion ..208/136 3,624,176 11/1971 Lhonore et al. ..260/683 Primary Examiner-Delbert E. Gantz Assistant ExaminerC. E. Spresser AttorneyArnold Robinson [57] ABSTRACT 19 Claims, No Drawings CATALYTIC STEAM CRACKING OF HYDROCARBONS AND CATALYSTS THEREFOR temperature above 800C in the cracking zone. Using a light naphtha as feed, a typical steam cracker produces methane and hydrogen 18 percent, ethylene 32 percent, ethane 5 percent, propylene 18 percent, butadiene 5 percent, butylene 4 percent, and gasoline/fuel oil 18 percent (percent by weight of feed).

The high temperature and large heat-flux in the cracking zone makes great demands of the materials of construction of the reactor. Furthermore, the required correlation between space velocity, temperature distribution, pressure drop in the system, and linear velocity is relatively costly, requiring considerable pilot-plant evaluation work.

It is also known to manufacture unsaturated hydrocarbons by catalytic cracking of higher saturated hydrocarbons at temperatures of 500-700C, using silica-alumina catalysts. However, these processes are troubled by carbon deposits on the catalyst which require frequent removal during operation.

Other catalyst compositions for steam cracking of hydrocarbons have been proposed. These compositions include combinations of zirconium oxide and one or more of a number of other oxides among which are oxides of the rare earth metals, antimony oxide, and inacv vtive oxides rich in magnesium oxide. Further oxides which might optionally be included in the catalyst composition in small amounts are iron oxide, aluminum ox ide, copper oxide, calcium oxide, barium oxide, silicium oxide, and titanium oxide. These catalysts are claimed to operate without carbon deposition at rather low space velocities.

it is an object of the present invention to provide a catalytic process for the manufacture'of unsaturated hydrocarbons, such as ethylene, propylene, butylenes,

butadiene, and aromatics, from saturated hydrocarbons which gives improved yield and thermal efficiencies while being capable of operating at high space velocity without significant carbon deposition on the catalyst.

According to the present invention we provide a process for the manufacture of unsaturated hydrocarbons by a gaseous catalytic reaction wherein a feedstock substantially comprising saturated hydrocarbons is contacted at a temperature below l,000C and a pressure of 0.1-50 atm.abs. in the presence of added steam with a catalyst comprising a major proportion of at least one oxide of zirconium or hafnium together with at least 5 percent of active aluminum oxide as well as at least 5 percent of at least one oxide of manganese, chromium or iron, and a small amount not exceeding l0 -percentof at least one compound of an alkali metal or alkaline earth metal.

Further according to the present invention we provide a catalyst for the manufacture of unsaturated hydrocarbons from saturated hydrocarbons in the presence of steam comprising a major proportion of at least one oxide of zirconium or hafnium, together with at least 5 percent of active aluminum oxide, as well as at least 5 percent of one oxide of manganese, chromium, or iron, and a small amount not exceeding 10 percent of at least one compound of an alkali metal or alkalineearth metal. a

In a preferred embodiment of the invention, the process is carried out at a temperature in the range 200"900"C, preferably in the range 500 850'C. it is also preferred to use pressures in the range 1-15 atm.abs. measured at the reactor outlet.

The major component of the catalyst used in the A process according to the present invention is zirconium or hafnium oxide or both. This component should be present in an amount of at least 50 wt.% up to It should be noted that a catalyst substantially consisting of, for example, zirconium oxide is not very'practicable because such a catalyst does not possess adequate mechanical strength unless it is subjected to a heat treatment at high temperatures such as temperatures above l,000C. It has been found that the presence of active aluminum oxide in the catalyst composition facilitates its preparation so that a satisfactory strength can be obtained from a heat treatment at a temperature below l,000C. The reactive aluminum oxide is added during the preparation of the catalyst either as such or as a compound which on heating transforms into an active aluminum oxide such as for example precipitated aluminum hydroxide. The amount of active aluminum oxide is not very critical and an amount of at least 5 wt.% is satisfactory.,The catalyst may contain up to 30 wt.% of active alumina, 10 wt.% being the preferred level.

In addition, the catalyst used in the process accord ing to the present inventioncontains at least 5 wt.% up to about 40 wt.% of one or more of the oxides of manganese, chromium, or iron together with an alkali metal compound or an alkaline earth metal compound or both in a total amount of 0.1 to 10' wt.% calculated in the oxide. If an alkaline earth compound is present it ispreferred to have a compound of an alkali metal present also. The use of a potassium compound in an amount of 0.3 to 7 wt.% calculated as the oxide is especially preferred.

When a catalyst composition in accordance with the products. Suitable saturated hydrocarbons include methane, ethane, propane, butane as well as liquid hydrocarbons such as light naphtha and even crude oil. Our process and catalyst readily tolerate the presence of sulphur which is even desirable since it can passivate the free metal surfaces in the reactor. The sulphur may -made on the equipment are accordingly reduced,

resulting in lower capital costs and also in reduced vulnerability of materials during operation. The design/operating requirements are less stringent, giving much greater flexibility and safety. Furthermore, conversion efficiencies are improved, giving higher production rate and higher yields of the desired unsaturated hydrocarbons.

in order that the invention should be better understood, it will now be described in further detail with reference in particular to the following examples:

PREPARATION OF CATALYSTS A. Catalyst comprising A1 -ZrO -Cr O K O A suspension was prepared of 600 g ZrO in 6 1 water at 65C and 370 g Cr(NO -9 H 0 and 1,840 g Al(NO:,) H O then dissolved therein. To this was 0 added 1,518 g NH HCO in 1 1 water at 65C, the resulting precipitation taking 25 minutes. The mixture was then stirred for one hour before filtering, and the collected precipitate washed with 6 1 water. This precipitate was then dried for 16 hours at 120C followed by 1 hour at 400C.

. The dried precipitate was mixed with 37 g graphite and 28 g cellulose fiber and ground for 6 hours in a ball mill, after which the mixture was tabletted. The tablets were then calcined for 2 hours at 850C.

1 17 g of these tablets were impregnated using a solution of 240 g KNO dissolved in 500 ml water, and then calcined for a further 2 hours at 400C.

The resulting catalyst A had the following composition (percentages by weight):

25% A1 0 61% ZrO 7% Cr O 7% K 0 B. Catalyst comprising A1 0 ZrO MnO K 0 A suspension of 56 kg ZrO in 1,000 l of deionized water at 65C was prepared and 108 kg Mn(NO ),-4 H 0 and 100 kg Al(NO '9 H O dissolved therein. 145

kg Nl'Ll-lCO was added to this over 1 hour and thereafter stirred for 12 hours. After adding a further 200 l of water the mixture was filtered in a pressure filter. The filtrate was dried for 12 hours at 200C whilst thoroughly blown by air, after which it was crushed and dried for a further two hours at 300C. The resulting dried product was mixed with 4 wt.% graphite and 3 wt.% cellulose fiber and tabletted in the form of hollow cylinders 7 mm high with an id. of6 mm and an o.d. of 13 mm, the tablets then being calcined for two hours at 800C. The cylindrical tablets were impregnated using a solution of 50 wt.% KNO in water, then heated for one hour at 80C and finally for 1 hour at 500C.

The resulting catalyst 13 had the following composition (by weight) 13% Al O 52% ZrO 27% MnO 8% K 0.

Further catalysts were prepared by similar methods but substituting one or more constituents giving catalysts of the following compositions:

C 13% A1 0 53% ZrO 27% MnO 7% Cs O 14% A1 0 56% ZrO 24% Fe O 6% K 0 E 14% A1 0 52% Tio 28% MnO 6% K 0 (Comparative Catalyst) F 14% A1 0 51% ZrO 28% MnO 3% BaO 4% K 0 These catalysts were evaluated in a small tube reactor (Reactor One) holding 125 ml catalyst. To this was fed a mixture of 2 parts naphtha and 1 parts water to give an eventual steam-naphtha weight ratio of 0.5. The naphtha had a weight composition of 24.1 percent isopentane, 53.6 percent n-pentane, 13.5 percent iso-hexane, 5.6 percent n-hexane, and 3.2 percent aromatics.

The naphtha-water feed was first passed through a preheater and then through the reactor, the space velocity being 4.2 liq. vol./vol. catalyst/h. The feed passed downwards through the reactor, the temperature at the top of the catalyst bed being 590C and the tempera ture at the center and at the bottom of the bed being 750C. The reactor effluent was quenched by water injection in the reactor outlet and the composition of the effluent product gas determined on a gas-chromatograph. The results of these investigations are shown in the accompanying table I.

Catalysts A, B, C, and D, which are in accordance with the present invention, all gave an almost complete conversion of the hydrocarbon feed with about 1 percent or less unconverted hydrocarbon feed in the product. Catalyst E, which is not in accordance with the present invention, gave a complete conversion right from the start, however, there was a gradual increase in unconverted hydrocarbon feed in the product, and after hours operation 20 percent of the hydrocarbon feed passed the catalyst almost unchanged. In the experiment with catalyst F, which is in accordance with the present invention, the conversion was incomplete from the start, however, after a few hours operation the conversion became complete and during the remaining part of the experiment the amount of unconverted hydrocarbon feed in the product was insignificant.

Because of unrealistic linear velocities of feed and product in a small tube reactor, the results are not representative as far as regards the yields of unsaturated hydrocarbons. Therefore, in order to obtain a more realistic evaluation of a catalyst in accordance with the present invention, catalyst B was tested in a pilot plant reactor (Reactor Two) having a height of 6 m and an internal diameter of 0.09 m. A series of oilfired burners were provided to heat the reactor. To this reactor was fed a feed of 200 kg/h of naphtha of the same composition as before, together with 120 kg/h steam (i.e., a steam-naphtha ratio of 0.6). The inlet pressure was 7 kg/cm, the outlet pressure 0.3 kg/cm, inlet temperature 500C and outlet temperature 825C. The heat flux at the inner reactor wall was 80,000 Kcal/mlf The results of investigations using 36 l of catalyst B in this reactor are shown in table II. Although a very high space velocity of 8.6 liq.vol./v0l.catalyst/h was used in this experiment only insignificant amounts of unconverted hydrocarbon feed appeared in the product, the liquid product consisting mainly of aromatics.

TABLE 1 (REACTOR ONE) Experiment No. 1 2 3 4 5 6 Catalyst A B C D E F Duration of expcriment,hrs. 138 240 66 200 120 325 Inlet pressure, atm.abs. 1.2 1.2 2.6 1.2 1.2 1.2 Space velocity, liq.vol./ vo1.cat./l\ 4.2 4.2 4.2 4.2 4.2 4.2 Yield at start: C 14 wt.% of feed 12.4 13.7 11.5 11.4 10.2 14.0 C li wt.% of feed 13.8 9.3 12.8 10.0 9.5 10.9 Liquid Product vol.% of feed 1.3 0 0 0 0 5.0 Yield at end: C,1-1,, wt.% of feed 12.4 14.4 10.7 10.3 10.2 Q11 wt.% of feed 9.8 10.7 9.5 8.3 9.5 Liquid product vol.% of feed 0.3 0.6 0.8 '0 20 0.1

+ Mainly unconverted hydrocarbon feed TABLE II (REACTOR TWO) Experiment No. 7 Catalyst B Duration of experiment, hrs. 100 lnlet pressure, atm.abs. 8 Outlet pressure, atm.abs. 1.3 Space velocity, liq.vol./vol.cat./h 8.6 Yield:

C,H wt.% of feed 31.5

C,H wt.% of feed 4.5

C511,, wt.% of feed 20.0

- C.H wt.% of feed 8.0 CM wt.% of feed 70 Liquid product, wt.% of feed 8.0

* Mainly aromatics What is claimed is:

I and/or iron and 0.1-l0 wt.% of at least one compound of an alkali metal or an alkaline earth metal.

2. A process according to claim 1, wherein the reaction is carried out at a temperature in the range 3. A process according to claim 2, wherein the reaction is carried out at a pressure of latm.abs. measuredat the reactor outlet. 7

4. A process according to claim 1, wherein the reaction is carried out at a temperaturein the range 5. A process according to claim 1, wherein the feedstock consists entirely of a saturated hydrocarbon or a mixture of saturated hydrocarbons.

6. A process according to claim 1, wherein the feedstock comprises a major proportion of saturated hydrocarbons and a minor proportion of unsaturated hydrocarbons.

7. A process according to claim 1, wherein the reaction is carried out in the presence of sulfur.

8. A process according to claim 7, wherein the sulfur is added to the feedstock in the form of free sulfur, hydrogen sulfide, carbon disulfide or an organic-sulfur compound.

9. A process according to claim 7, wherein sufficient steam is added to give a weight ratio of steam to hydrocarbon feedstock in the reactor of 0.1-1 .0.

10. A process according to claim 1, wherein sufficient steam is added to give a weight ratio of steam to hydrocarbon feedstock in the reactor of 001-10.

11. A process according to claim 10, wherein the ratio of steam to hydrocarbon feedstock is 0.1-1.0.

12. A process for the manufacture of unsaturated hydrocarbons by a gaseous catalytic reaction wherein a feedstock substantially comprising saturated hydrocarbons is contacted at a temperature in the range 500850C and a pressure in the range l-15 atm.abs. measured at the reactor outlet in the presence of added steam with a catalyst comprising 50-80 wt.% zirconium and/or hafnium oxide, together with 5-30 wt.% active alumina,- as well as 5-40 wt.% of at least one oxide of chromium manganese and/or iron 'and 0.3-7.0 wt.% of at least one compound of an alkali metal and/or alkaline earth metal.

'13. A process according to claim 12, wherein the feedstock consists entirely of a saturated hydrocarbon or a mixture of saturated hydrocarbons.

14. A process according to claim 12, wherein the feedstock comprises a major proportion of saturated hydrocarbons and a minor proportion of unsaturated hydrocarbons.

15'. A process according to claim 12, wherein the reaction is carried'out in the presence ofsulfur.

16. A process according to claim 15, wherein the sulfur is added to the feedstock in the form of free sulfur, hydrogen sulfide, carbon disulfide or an organic sulfur compound. I

17. A process according to claim 15, wherein sufficient steam is added to give a weight'ratio' of steam to hydrocarbon feedstock in the reactor of-0.ll .0.

18. A process according to claim 12, wherein sufficient steam is added to give a weight ratio of steam' to hydrocarbon feedstockin the reactor of 0.01 10.

19. A process according to claim '18, wherein the ratio of steam to hydrocarbon feedstock is 0.1-1.0. 

2. A process according to claim 1, wherein the reaction is carried out at a temperature in the range 200*-900*C.
 3. A process according to claim 2, wherein the reaction is carried out at a pressure of 1-15 atm.abs. measured at the reactor outlet.
 4. A process according to claim 1, wherein the reaction is carried out at a temperature in the range 500*-850*C.
 5. A process according to claim 1, wherein the feedstock consists entirely of a saturated hydrocarbon or a mixture of saturated hydrocarbons.
 6. A process according to claim 1, wherein the feedstock comprises a major proportion of saturated hydrocarbons and a minor proportion of unsaturated hydrocarbons.
 7. A process according to claim 1, wherein the reaction is carried out in the presence of sulfur.
 8. A process according to claim 7, wherein the sulfur is added to the feedstock in the form of free sulfur, hydrogen sulfide, carbon disulfide or an organic sulfur compound.
 9. A process according to claim 7, wherein sufficient steam is added to give a weight ratio of steam to hydrocarbon feedstock in the reactor of 0.1-1.0.
 10. A process according to claim 1, wherein sufficient steam is added to give a weight ratio of steam to hydrocarbon feedstock in the reactor of 0.01-10.
 11. A process according to claim 10, wherein the ratio of steam to hydrocarbon feedstock is 0.1-1.0.
 12. A process for the manufacture of unsaturated hydrocarbons by a gaseous catalytic reaction wherein a feedstock substantially comprising saturated hydrocarbons is contacted at a temperature in the range 500*-850*C and a pressure in the range 1-15 atm.abs. measured at the reactor outlet in the preseNce of added steam with a catalyst comprising 50-80 wt.% zirconium and/or hafnium oxide, together with 5-30 wt.% active alumina, as well as 5-40 wt.% of at least one oxide of chromium manganese and/or iron and 0.3-7.0 wt.% of at least one compound of an alkali metal and/or alkaline earth metal.
 13. A process according to claim 12, wherein the feedstock consists entirely of a saturated hydrocarbon or a mixture of saturated hydrocarbons.
 14. A process according to claim 12, wherein the feedstock comprises a major proportion of saturated hydrocarbons and a minor proportion of unsaturated hydrocarbons.
 15. A process according to claim 12, wherein the reaction is carried out in the presence of sulfur.
 16. A process according to claim 15, wherein the sulfur is added to the feedstock in the form of free sulfur, hydrogen sulfide, carbon disulfide or an organic sulfur compound.
 17. A process according to claim 15, wherein sufficient steam is added to give a weight ratio of steam to hydrocarbon feedstock in the reactor of 0.1-1.0.
 18. A process according to claim 12, wherein sufficient steam is added to give a weight ratio of steam to hydrocarbon feedstock in the reactor of 0.01-10.
 19. A process according to claim 18, wherein the ratio of steam to hydrocarbon feedstock is 0.1-1.0. 